In the Smoky Mountains of North Carolina, Rackham student Matthew Chatfield carefully inspects each salamander before he snaps off their tails with his hands and brings the tails back to his lab in the Ecology and Evolutionary Biology Department.
Chatfield returned from his third trip to North Carolina in September, where he was collecting DNA samples from three different species of salamanders: the red-cheeked salamander, the Southern gray-cheeked salamander and a hybrid salamander, which is a cross between the red and gray-cheeked species.
Hybrids come about when the two purebred forms mate.
Chatfield set up a campsite atop a mountain ridge in the Smoky Mountains during the summer to collect salamander tails, which regenerate when removed. Chatfield wanders the ridge looking for the salamanders, armed a thermos full of dry ice, which he uses to preserve and transport the tails.
The red and gray-cheeked salamanders are found at the highest elevations of the mountain range – about 4,500 feet – but inhabit separate areas of the ridge. The hybrids inhabit an eight-mile stretch of land that overlaps these areas, known as the hybrid zone. This stretch is known as the hybrid zone.
The term “hybrid” refers to a cross between two species.
At the lab on campus, the hybrid salamander tails are stored in a negative-80-degree freezer.
The salamanders look exactly alike except for the bright red cheeks of the red-cheeked species.
“The coloration of the cheeks is a warning to predators,” Chatfield said. He said the salamander secretes a slimy substance through its skin when attacked.
The hybrid species resembles the other two species but has reddish-gray cheeks. Chatfield said the hybrid species is a “cryptic” hybrid because he has to carefully inspect the cheeks to determine if the salamander is a hybrid. The hybrids are increasingly populating the region.
Chatfield is currently working to extract DNA to determine which genes are responsible for the color of the salamanders’ cheeks. He hopes to learn about the environment of the hybrid zone and the evolutionary value of the red pigmentation gene. More generally, he wants to know why this useful genetic trait isn’t more prevalent in other salamander species.
Scientific studies like Chatfield’s help shed light on evolution.
The movement of a gene from one species to another is known as introgression and can result in a hybrid species. Selective breeding or the mating of two different species also creates hybrid animals.
Many hybrid species occur naturally, like the zeedonk – a cross between a zebra and a donkey. But other hybrids are produced through human breeding techniques. Examples include tigons, a cross between a male tiger and a female lion, and beefalos, a cross between an American bison and a domestic cow.
Tucker and others in her field of evolutionary biology refer to these hybrid animals as “charismatic mega-fauna.” She said these animals are the most popular example of a hybrid to many people because of the media attention they receive when they are bred.